An image capturing device, equipped with a correction means capable of correcting a captured image (an image of a subject such as a white board, a book, etc. captured by the device) as if the subject were shot from the front even when the subject is shot from a direction oblique to the front of the subject, is well known today. Such a correction means makes the correction by detecting the three-dimensional shape of the subject based on the captured image of the subject. A portable digital camera equipped with such a correction means has been disclosed in, for example, FIG. 1, etc. of Japanese Patent Provisional Publication No. HEI09-289611 (hereinafter referred to as a “document No. 1”).
A technique for detecting the three-dimensional shape of the subject as parameters required by the aforementioned correction means has been disclosed in the tenth paragraph, FIG. 3, etc. of Japanese Patent Publication No.3282331 (hereinafter referred to as a “document No.2”). Specifically, the document No. 2 discloses a three-dimensional shape measurement device of a stationary type. The device extracts slit beams projected on the subject by subtracting a slit-beamless image (obtained by shooting the subject on which no slit beams are projected) from a slit-beamed image (obtained by shooting the subject on which the slit beams are projected), and detects the three-dimensional shape of the subject based on the extracted slit beams.